CaV 3.1 and CaV 3.3 account for T-type Ca2+ current in GH3 cells

• Autor(a) principal: Mudado,M.A.
• Data de Publicação: 2004
• Outros Autores: Rodrigues,A.L., Prado,V.F., Beirão,P.S.L., Cruz,J.S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Brazilian Journal of Medical and Biological Research
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2004000600020
• topic: Calcium channel; T-type; Electrophysiology; RT-PCR; GH3 cells

T-type Ca2+ channels are important for cell signaling by a variety of cells. We report here the electrophysiological and molecular characteristics of the whole-cell Ca2+ current in GH3 clonal pituitary cells. The current inactivation at 0 mV was described by a single exponential function with a time constant of 18.32 ± 1.87 ms (N = 16). The I-V relationship measured with Ca2+ as a charge carrier was shifted to the left when we applied a conditioning pre-pulse of up to -120 mV, indicating that a low voltage-activated current may be present in GH3 cells. Transient currents were first activated at -50 mV and peaked around -20 mV. The half-maximal voltage activation and the slope factors for the two conditions are -35.02 ± 2.4 and 6.7 ± 0.3 mV (pre-pulse of -120 mV, N = 15), and -27.0 ± 0.97 and 7.5 ± 0.7 mV (pre-pulse of -40 mV, N = 9). The 8-mV shift in the activation mid-point was statistically significant (P < 0.05). The tail currents decayed bi-exponentially suggesting two different T-type Ca2+ channel populations. RT-PCR revealed the presence of a1G (CaV3.1) and a1I (CaV3.3) T-type Ca2+ channel mRNA transcripts.